Not to be semantically confused with :
Dill (Anethum graveolens) [an Umbellifer (Apiaceae) with similar name used as a herb in cooking]
Many similarities to : Hoary Cress (Lepidium draba) but that has leaves with fewer larger teeth, the upper leaves have auricles extending backwards each side of the stem. The flower clusters larger and more open with the flowers themselves twice as large at 5-6mm.
It is a much-branched, tall greyish-green plant with panicles of tiny white flowers in small globular clusters at the ends of each termination. Lower leaves are larger and have small teeth, uppermost leaves/bracts narrow lanceolate and much shorter. It is perennial with rhizomatous roots which spread to form great swathes in damp places near the sea and/or near the riparian zone of riverbanks and streams.
In some parts of the World this is a controlled weed (such as Tasmania). Even in the UK it can spread rather uncontrollably.
The roots of Dittander are able to tap water at considerable depth because the extensive root system reaches down up to 2 metres. Because Dittander prefers a seaside location, it is thus exposed to halogens in the soil which may have arrived by past sea-inundations, for example from large storm surges, large tides, or from tsunamis which are not unknown in the UK. And because the roots reach 2m down, they may already have reached the halocline beneath the soil surface which, near the sea, sits just below the average level of the sea water. In uptaking water Dittander absorbs the halogenated compounds, mainly sodium chloride and sodium bromide. Dittander would rather get rid of excess chlorine and bromine and does so by emitting
Methyl Chloride, CH3Cl and
Methyl Bromide CH3Br with maximum emissions occurring at midday in the sunshine, exceeded only by the peak emissions at senescence of the plant. It is a major source of these methyl halides, which are partly responsible for the catalytic destruction of ozone in the upper atmosphere. When an ozone hole is created at the poles of the Earth, dangerous amounts of ultraviolet light from the sun is allowed onto the Earths surface.
The glucosinolate Sinigrin is present in large amounts, which is the source of the mustard oils and other sulfur-containing compounds found in Dittander. The main volatile components of the seed and roots of Dittander comprise Allyl-Isothiocyanate,
Butylsothiocyanate, whilst the leaves contain Allyl-Isothiocyanate and
1-Cyano-2,3-EpiThioPropane as the main volatiles.
The leaves have a very bitter and peppery taste (due to the poisonous Glucosinolates present) which only become edible after extensive boiling and soaking, so, in the UK, are not worth the considerable effort required.